In manufacturing steps of a semiconductor device such as a semiconductor integrated circuit element, an active element such as a MIS transistor, a passive element such as a capacitative element, and a wiring layer, where these functional elements are mutually connected are formed on the principal surface of a semiconductor substrate (for example, semiconductor wafer).
When the functional elements, the wiring layer and an insulating layer to provide isolatation among the other elements are formed on the substrate, a chemical mechanical polish (CMP) method is applied for thinning and planarizing.
During the CMP processing, abrasive agent (slurry) is supplied onto the surface of a polishing pad (abrasive cloth) located on a disk-shaped polishing table (surface table, platen), the polishing table is rotated, a rotating object to be polished, that is the polished surface of the semiconductor substrate, is contacted to the polishing pad, and the surface is polished.
In such a CMP processing, the polishing pad located on the polishing table needs to have a structure that has high retentiveness of abrasive agent supplied onto the surface (polished surface), the abrasive agent must be efficiently moved all over the surface of the polishing pad, and further product material generated at polishing must be efficiently discharged.
As a result, the polishing pad is equipped with a foam structure on its surface (polished surface) or is equipped with high retentiveness of the abrasive agent by roughening the surface with dressing processing.
The foam part forms micropores, and keeps abrasive particles in the abrasive agent.
As a polishing pad that has the foam structure, there is, for example, foamed polyurethane having an independent foam structure. It is formed by mixing and stirring an isocyanate group containing chemical compound, active hydrogen containing chemical compound and foaming agent, injecting the mixture into a mold, heating and hardening it to obtain a molded body, and cutting it into a prescribed thickness. (For example, refer to Japanese Patent Application laid-open No. 2002-194104 and No. 2006-77044.)
On the other hand, it has also been proposed to allocate plural concave portions (holes) on the sheet-like formed surface of the polishing pad, that is the polished surface, to retain the abrasive agent. (For example, refer to the United States published application No. 2004-014413 and Japanese Patent Application laid-open No. Hei-8-229805.)
In addition, a structure in which a groove is allocated on the polishing surface of the polishing pad to improve the mobility of the abrasive agent and efficiently discharge the product material generated at polishing has been proposed. (For example, refer to Japanese Patent Application laid-open No. 2003-103470 and No. Hei-8-229805.)
In addition, it has also been proposed to allocate both the concave portions (holes) and the groove on the polishing surface of the polishing pad. (For example, refer to Japanese Patent Application laid-open No. 2002-160153 and No. 2004-140178.)
The surface of the polishing pad (the polishing surface) may not always be formed homogeneously due to factors such as material composition, stirring condition or processing temperature condition. (For example, refer to Japanese Patent Application laid-open No. 2002-92593 and No. 2005-19886.)
In addition, contamination may occur during processing such as stirring, mixing or molding. As such, the polishing pad may have malformed portions.
It is difficult to utilize a polishing pad including a defective part resulting from malformation of the polishing pad in the CMP process.
On the other hand, prior to performing the CMP processing, it is proposed to optically examine the surface state of the polishing pad by placing the polishing pad on the polishing table, and having a worker remove the defect part depending on the examination result. (For example, refer to the U.S. Pat. No. 6,650,408.)
However, the most cases in which the worker can remove the defective part prior to the CMP processing are limited to when the defect is due to contamination attached onto the surface of the polishing pad.
If defective parts of the pad are caused by the manufacturing of the pad and the defective part is within the pad, where it is difficult to remove, such as inside the polishing pad or inside the surface part, the polishing pad may be used rather than disposed.
As a result, the conventional polishing pad will not be used effectively, resulting in inefficiency and increased cost to the manufacturing process of the semiconductor device.